The hyoscyamine content of leaves and root samples of Hyoscyamus reticulatus L. from Bulamk, Mus in east Anatolia, Turkey, was determined by capillary GC-MIS to be 0.036 +/- 0.004% in the leaves and 0.056 +/- 0.011% in the roots as the predominant compound. Sopolamine was only detected in trace amounts. These findings are in accordance with reports on hyoscyamine content in Hyoscyamus species. The limit of detection was 3.125 mug/mL and the limit of quantification was 6.25 mug/ml, for hyoscyamine. This method has been shown to be linear and sensitive.